1. Field of the Invention
The present invention relates to an analyzing device for analyzing gas exhausted from cars.
2. Description of the Prior Art
In order to reduce a distance (l in FIG. 3) from a sample-inlet of a dilution tunnel 6 for diluting exhaust gas from cars with air which is in a decompressed condition, that is to say air within a low-pressure testing room, to an exhaust-gas analyzer 8, the exhaust-gas analyzer has been arranged in the low-pressure testing room. That is to say, a construction as shown in FIG. 3 has been used. Referring to FIG. 3, reference numeral 1 designates a low-pressure testing room, reference numeral 2 designates atmosphere pressure, reference numeral 3 designates a decompression blower, reference numeral 4 designates a car, reference numeral 5 designates a chassis dynamometer, reference numeral 6 designates a dilution tunnel, reference numeral 7 designates air, reference numeral 8 designates an analyzer, reference numeral 9 designates an overflow line, reference numeral 10 designates a zero gas passage, reference numeral 11 designates a span gas passage, reference numeral 12 designates a bag sample passage, and reference numeral 13 designates a valve.
When HC (hydrocarbon) is measured, if the temperature is reduced, certain kinds of HC do not assume a gaseous state, so that it is necessary to maintain the temperature high and therefore, l has been reduced. For example, such is the case when an HC analyzer is used as an exhaust-gas analyzer.
An exhaust-gas analyzer for use with a car is influenced with respect to its analytical sensitivity by a fluctuation in atmospheric pressure. Although the accuracy of the exhaust-gas analysis is not influenced by the fluctuation of atmospheric pressure in nature at the same altitude, if atmospheric pressure is reduced to about a half atm. as occurs in the low-pressure testing room, for example, the pressure of air is reduced to 460 to 400 mmHg, as a result, the accuracy of the exhaust-gas analysis is diminished. The conventional analyzer has not taken measures for solving the above-described problem. Therefore, according to the known method, the measurement is carried out under a condition in which the accuracy is reduced in dependence upon a degree of the setting of pressure in the low-pressure testing room, or, in which pressure is calibrated (this is not easy) and then data is read.